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Updated: Apr 10, 2026
High-throughput Gene Tagging in Trypanosoma brucei
Published on: August 12, 2016
Kozak sequences regulate gene expression in Trypanosoma brucei
Philip Stettler1, Marina Cristodero1, Norbert Polacek1
1Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern 3012, Switzerland.
Abstract:
The Kozak consensus sequence around the AUG start codon of mRNAs allows efficient cytosolic translation initiation in eukaryotes. It has not yet been investigated in the parasitic protozoan Trypanosoma brucei. mRNAs in T. brucei and other kinetoplastids are exclusively produced by polycistronic transcription. The levels of individual mRNAs can, therefore, not be regulated by transcription. Here, we show that in contrast to yeast and animals, no Kozak consensus sequence could be found in the total mRNA population of T. brucei or other kinetoplastids. However, when analyzing the subpopulation of constitutively expressed trypanosomal mRNAs encoding highly abundant proteins, a Kozak motif with a strong bias toward a +5C was detected. We tested how variants of the Kozak sequence influence the translation levels of a reporter protein. Using this in vivo approach, "weak" and "strong" Kozak sequences resulting in "low" and "high" translation levels could be defined. The "strong" sequences required a +5C and allowed initiation from CUG instead of AUG. We, therefore, suggest that in T. brucei, due to the lack of transcriptional control, Kozak sequences contribute to the regulation of protein levels. Moreover, we provide a new way to modulate protein abundance in transgenic trypanosomes in a predicted way.
Insights
In Trypanosoma brucei, a specific Kozak sequence motif, particularly a +5C, influences protein levels. This finding offers a novel method for controlling protein abundance in transgenic trypanosomes.
Area of Science:
- Molecular Biology
- Parasitology
- Genetics
Background:
- The Kozak consensus sequence is crucial for efficient translation initiation in eukaryotes.
- Investigating the Kozak sequence in Trypanosoma brucei is important due to its unique mRNA processing (polycistronic transcription).
- Transcriptional regulation of individual mRNAs is absent in T. brucei, necessitating post-transcriptional regulatory mechanisms.
Purpose of the Study:
- To investigate the presence and function of Kozak consensus sequences in Trypanosoma brucei.
- To determine if Kozak sequences contribute to post-transcriptional regulation of protein levels in T. brucei.
- To explore the potential of manipulating Kozak sequences for controlling protein expression in transgenic trypanosomes.
Main Methods:
- Analysis of total and subpopulation mRNA sequences in T. brucei and other kinetoplastids.
- In vivo reporter assays to assess the impact of different Kozak sequence variants on translation levels.
- Comparison of translation initiation from AUG and CUG codons influenced by Kozak sequences.
Main Results:
- No general Kozak consensus sequence was found in the total mRNA population of T. brucei.
- A specific Kozak motif with a +5C bias was identified in constitutively expressed trypanosomal mRNAs.
- Defined "weak" and "strong" Kozak sequences correlating with low and high translation levels, respectively.
- Strong Kozak sequences facilitated initiation from CUG codons.
Conclusions:
- Kozak sequences, particularly the +5C, play a role in regulating protein levels in T. brucei, compensating for the lack of transcriptional control.
- The identified Kozak motifs provide a novel strategy for predictable modulation of protein abundance in transgenic trypanosomes.
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